Circuit weight training is a specific type of resistance training that incorporates light weights and short rest intervals, and results in beneficial cardiorespiratory and musculoskeletal adaptations. One of the most important adaptations appears to be reduction of arterial pressure, especially for individuals who may be prehypertensive. The overall goal of this project is to document physiological mechanisms modulating arterial pressure and arterial pressure regulation in response to circuit weight training in prehypertensive young adults. The proposed research will test the hypotheses that circuit weight training decreases arterial blood pressure, baseline sympathetic neural activity and arterial stiffness, and increases parasympathetic cardiac control and cardiovagal baroreflex sensitivity in direct proportion to exercise training duration. In order to test these hypotheses, the following specific aims will be addressed: Determine the effects of a 12-week circuit weight training program on 1) resting arterial pressure; 2) sympathetic neural activity; 3) respiratory sinus arrhythmia and cardiovagal baroreflex sensitivity; and 4) central and peripheral arterial stiffness. In conjunction with specific goals of the AREA program, comprehensive research experience will be made available to talented undergraduate students who will serve as assistants. To accomplish these specific aims, the following tests will be performed before, and then after 4, 8, and 12 weeks of structured circuit weight training: 1) with subjects in the seated position, blood pressure will be measured three times from the arm using an automated sphygmomanometer, and the average systolic and diastolic pressures will be recorded; 2) with subjects in the supine position, muscle sympathetic nerve activity will be measured directly using the microneurography technique, and blood will be drawn from an anticubital vein for assessment of plasma catecholamine concentrations; 3) subjects will control their breathing at 15 breaths per minute. R-R intervals will be converted to the frequency domain, and respiratory sinus arrhythmia will be assessed as the integrated area under the respiratory frequency band of the power spectrum. Spontaneous baroreflex sensitivity will be assessed in both time and frequency domains. Dynamic baroreflex sensitivity will be assessed from R-R interval responses to arterial pressure elevations during release from Valsalva strain; 4) Using bidirectional transcutaneous Doppler ultrasound probes, pulse waves velocities between the left common carotid artery and the left femoral artery, and the left femoral artery and the superior dorsalis pedis artery will be obtained. Pulse wave velocity will be calculated as the distance between measuring sites divided by the change in time intervals. Values attained from the carotid to femoral artery will be taken as an index of central stiffness, while values from the femoral to superior dorsalis pedis artery will be taken as an index of peripheral stiffness. Reversing or controlling prehypertension through non-pharmacological means will decrease future overall health care costs. Promoting physical activity as a lifestyle choice to decrease arterial pressure will decrease the prevalence of cardiovascular disease and stroke, which are the first and third leading causes of death in the United States. [unreadable] [unreadable] [unreadable]